The present invention relates to noise management, and more particularly, to sensor measurement adjustments due to noise signatures of line noise coupled with a sensor signal.
Sensors are used in a variety of settings, such as monitoring processes in industrial process facilities, in order to generate data signals. These data signals can be transmitted to circuitry that performs digitizing, analysis, communication relay, or other functions. For data acquisition, quickly updated but highly accurate process measurements are generally desirable. In the field of industrial process measurement, updates generally refer to information transmissions to a control room or other control equipment, and a given process update can include a number of discrete sensor measurements bundled together, averaged together, etc.
However, during operation, line noise can often become coupled to data signals from a sensor. For example, power sources (or other noise sources) located near wires carrying sensor data signals can couple line noise to the data signals. Line noise from power sources typically produces an AC noise signal that has a frequency of about 60 Hz in the United States and about 50 Hz in Europe. Line noise can be especially problematic with certain types of sensors (e.g., temperature sensors) that are typically located remotely from processing circuitry, and have wires connecting the sensor to the processing circuitry. Line noise coupled to sensor data signals is undesirable, and presents a risk of measurement error.
Prior art industrial process measurement systems have provided a 50/60 Hz switch, that allows manual selection of either 50 Hz or 60 Hz filtering of sensor signals at the time of installation or maintenance to reduce line noise effects during later operation. This approach can be effective for many applications. However, the filtering selections are limited to predefined choices, and unpredictable noise sources can still present a risk of measurement error. Moreover, filtering selection using a manual switch presumes that a noise source is well-defined and known to an operator during system installation or maintenance. This presents a risk of operator error during setup, if the operator makes an incorrect filtering selection, and also can increase the time and effort required for system setup.
Furthermore, prior art industrial process measurement systems with a filtering selection switch use constant filtering. However, constant filtering (e.g., with a decimation filter) can reduce an update rate, and can increase power consumption by the process measurement system. Slower update rates are generally less desirable than faster ones. Also, industrial process measurement systems, particularly those that communicate wirelessly, can be powered by batteries or energy harvesting systems for which low power consumption is desirable.